1. Field of the Invention (Technical Field)
The present invention relates to a bearing and drive assembly for trenchers, and more particularly to a bearing and drive assembly for rock or hard soil trenchers.
2. Background Art
Chain drive ditchers or trenchers are used for excavating in both sandy or soft soils and rocky or hard soils. U.S. Pat. No. 4,626,032 to Harris, et al., describes a ditcher for excavating hard soils. Problems with current ditchers and trenchers include that the drive assembly for moving the endless chain, during excavation, is exposed to dirt and debris, wearing out parts of the assembly, or is equipped with bushings that likewise do not keep harmful debris from entering into the gear box. This shortens the life of the drive assembly, increases the amount of maintenance and causes the overall efficiency of the ditcher or trencher to decrease as the parts of the assembly wear out. This problem is exacerbated when digging through rocky or hard soils due to the increased load on the mechanism and vibration.
Most endless chain trenchers take power from the engine to a flywheel. Power is transmitted from the flywheel clutch to one or more hydraulic pumps by a driveline and U joint assembly. Hydraulic power is supplied by the pumps to hydraulic motors which in turn rotate the head shaft drive assembly. In the center of the head shaft are drive sprockets that rotate the endless chain assembly.
Existing trenchers do not have adequate seals to keep dirt or debris out of the hood bushings. Additionally, they do not have adequate seals to keep grease on the bushings. Most bushings for drives must be lubricated by applying grease externally to the bushings. Once the grease is on, there is nothing to keep it on the bushing or to keep dirt and debris from collecting on the grease. The bushings themselves do not have enough surface area to withstand the load and the vibration of the boom.
There are similar problems with the head shaft and bearing assemblies. The lack of sealing allows dirt and debris to enter the head shaft boxes. Lubrication is accomplished by pumping grease through a tube to the hood bushings and head shaft bearings. The lower final drives are lubricated in the same manner.